Reoperations for acute prosthetic thrombosis and pannus: an assessment of rates, relationship and risk

Objective: Mechanical valvular prostheses have the advantage of longevity b ut carry a risk of thrombosis which is dependant on valve design, materials and host-related interface. While pannus is common to both biologic and me chanical valves, acute prosthetic thrombosis is mostly a complication of me chanical valves; therefore we investigated to find rates and risk of these obstructive complications. Methods: Between 1/1/70 and 31/12/97, 2680 patie nts received at least one mechanical prosthesis in the aortic or mitral or tricuspid position and a total of 3014 operations were performed. Follow-up included 18523 years and was 98% complete. Incidence rates, Kaplan-Meier e stimates, modeling of the hazard and multivariate analysis in the hazard do main were used in the analysis. Results: Overall survival was 76%, 64%, 51% , 38.5% and 29% at 5, 10, 15, 20 and 25 years, respectively. It was signifi cantly better in aortic than in mitral than in double prosthesis. 290 patie nts received a single reoperation, 37 a second, six a third and one a fourt h reoperation. Two-hundred and fifty-one of these reoperations were exclusi vely due to malfunction of mechanical prosthesis, nine to malfunction of bo th mechanic and biologic prostheses. Most frequent reoperative indications was dehiscence (133), pannus (48) and thrombosis (29). The linearized rate of reoperation's for pannus was 0.24%/patient per year, for valvular thromb osis 0.15 %/patient per year. The shape of the thrombotic hazard was consta nt (at random) and the relative risk 12 times higher for tricuspid prosthes is, seven times higher for mitral prosthesis. Multivariate analysis control ling for prosthetic position, age, sex and prosthetic size, showed a 67% ri sk reduction with larger prosthesis (>27 mm), a 69% risk reduction with the Sorin tilting disk prosthesis and an 83% risk reduction with the bileaflet prosthesis. Pannus hazard shows a delayed exponential rise and was two tim es higher in tricuspid and three times higher in mitral position. Multivari ate analysis showed a 50% risk reduction with larger prosthesis, an 11 time s higher hazard of old (caged-disk, caged ball) prosthesis and a three time s higher hazard of Lillehei-Kaster prosthesis. Reoperation for thrombosis h as a 62% perioperative (30 days) survival compared to 92% survival of pannu s reoperation. Conclusions: Mechanical valves have a low incidence of reope ration, mostly for prosthetic dehiscence. Pannus development is the next fr equent complication increasing with time since implant, therefore in this s eries it was related to old valvular models and tilting disk prosthesis, wi th longer follow-up. Acute thrombosis occurs significantly earlier than pan nus formation. Despite shorter follow-up we are therefore confident that bi leaflet prostheses are less prone to this complication and pannus is a rare early etiologic factor. Thrombosis has very high operative risk as compare d to pannus, justifying the present trend to thrombolysate selected cases. (C) 1999 Elsevier Science B.V. All rights reserved.